1. Field of the Invention
Exemplary embodiments of the present invention relate to a light emitting diode (LED) lighting apparatus using LEDs and, more particularly, to an LED lighting apparatus having a tube-type or channel-type optical housing.
2. Discussion of the Background
For a long time, a cold cathode fluorescent lamp, referred to as a “fluorescent lamp,” has been used as a lighting apparatus for brightening and illuminating interior spaces in commercial buildings, houses, and interior spaces in transportation means such as airplanes, automobiles, ships, trains, and subway trains. However, the cold cathode fluorescent lamp may have disadvantages such as a short life span, poor durability, limited range of light colors, and low energy efficiency.
Recently, similar to cold cathode fluorescent lamps, a tube-type LED lighting apparatus comprising a generally circularly-shaped, elongated light-transmissive tube and a plurality of LEDs arranged in the light-transmissive tube has been developed. Compared to a cold cathode fluorescent lamp, such a tube-type LED lighting apparatus may have advantages that include a longer life span, better durability, a wider range of light colors, and greater energy efficiency.
However, the conventional tube-type LED lighting apparatus also may be disadvantageous due to intrinsic characteristics of the LEDs used as a light source. Some of the characteristics include the considerably straight, slightly divergent light emitted from the LEDs that impinges on the circular surface of the tube, thereby producing a Lambertian light emission angular distribution pattern, i.e., a light emission angular distribution pattern with a narrow angular range. Accordingly, the conventional tube-type LED lighting apparatus may have many technical limits for replacing the conventional cold cathode fluorescent lamp when used for interior lighting.
Additionally, a channel-type LED lighting apparatus has recently been used. Here, a plurality of LEDs is longitudinally arranged in an elongated channel with an open front face instead of the tube as described above. The inner volume of the channel is filled with a light-emissive resin material, or a transparent glass or plastic is arranged on the front face of the channel. Due to the narrow angular distribution of light emission from an LED from its flat light emissive surface, the above channel-type LED lighting apparatus may be subject to serious light losses caused by the internal reflection of the channel, and such apparatus have been used chiefly as advertisement lighting for displaying letters, numerals, marks, logos, and symbols instead of lighting for brightening and illuminating interior spaces. Even for channel-type LED lighting apparatus used in advertisement lighting, the low light efficiency of the channel-type LED lighting apparatus may be a drawback. Accordingly, ways to reduce the light losses for the channel-type LED lighting apparatus are sought.
Other conventional tube-type and channel-type LED lighting apparatus employ an LED package article for emitting white light generated by a combination of a phosphor and an LED chip, particularly an LED chip emitting blue-colored light matched with an appropriate phosphor. However, as the operating on-time of the LED lighting apparatus increases, the phosphor located adjacent to the LED chip in the LED package article may degrade, thereby lowering the reliability of the LED lighting apparatus. Accordingly, improvements in LED lighting apparatus such as increasing its reliability by decreasing the degradation of the phosphor are desired.